In optical scanning systems, and in other applications, electromechanical resonators are used as modulators for causing periodic deflection of a light beam. It is desirable in certain optical scanning systems to produce beam deflection which varies as a sinusoidal function of time at a desired frequency. This can be achieved by a torsionally resonant system which includes a torsion rod with a mirror mounted thereon and means to sustain the torsional system in oscillation at the natural frequency thereof. A torsional resonator exhibits a high Q (quality factor) and can be sustained in sinusoidal oscillation by a simple electrodynamic drive means. The power requirements are small since it is only necessary to supply the losses arising from hysteresis, windage (air resistance), and the like. No bearings are required and the device has a long, maintenance free life.
A torsional resonator is desired for applications in which a relatively short axial dimension is required and a relatively long lateral dimension is permissible. Further, the performance of the resonator is to be substantially independent of the installation mounting or clamping arrangement. Additionally the resonator is to be of such design that it may be manufactured without requiring a high degree of dimensional precision of the parts and assembly.